The following correction was printed in the Guardian's Corrections and clarifications column, Thursday June 1 2006

Asphalt is made from bitumen, not cement

In 1824 an English bricklayer named Joseph Aspdin rediscovered one of the great secrets of the ancient world. Burning limestone and clay together at an incredible heat - more than 2,700 degrees fahrenheit - made the two minerals fuse together. Once cooled and ground into a fine ash, the resulting substance would, after mixing with water, set as hard as the Portland stone that gave it its name. And while his invention, portland cement, is seldom celebrated in the same breath as steam power or the spinning jenny or even the mass introduction of soap, it too - literally - laid a cornerstone of the modern industrial world.

Beloved of master builders, detested by their labourers and used by the Romans, cement supports the very ground beneath your feet and keeps the roof from crashing in; yet few outside the building trade spare the back-breaking bringer of toil much thought.

But maybe we should. Cement is one of the most environmentally hazardous materials in the world, adding more carbon dioxide to the atmosphere than the entire weight of the global airline industry. According to the Sustainable Development Commission, 4% of Co2 is caused by aviation. Depending on how conservatively you do the sums, cement-based building materials, including concrete and asphalt, account for between 5% and 10% of all carbon dioxide emissions. Finding an alternative product to cement would, therefore, make excellent environmental sense, especially if Britain is to meet the government's ambitious target of a 60% reduction in carbon dioxide emissions by 2050.

Now, it is possible, if one squints very hard, to imagine a world without the luxury of cheap air travel. Harder still, one without the convenience of a car. But a world entirely without cement lies further out of reach, in an untamed place shorn of Tarmac, airport runways, road bridges, skyscrapers, underground stations or modern reservoirs. Such is our dependence on the stuff.

But while the environmental impact of cement production has been known for ages - Dickens described in Great Expectations "the sluggish stifling smell" of the kilns - few call for it to be punitively taxed. Friends of the Earth, for instance, could not produce a single spokesperson to speak about cement's effect on climate change; and what environmental campaigns there are, such as the recent protests against a tyre-burning kiln in Rugby, focus on what is burned to generate the heat, not the cement itself. The consensus has it that we are stuck with cement.

Not so, say the influential environmental bloggers at worldchanging.org, who recently identified a "whole slew of viable alternatives" to both cement and concrete ... "[that] give some hope that a much greener (and potentially more sustainable) model for concrete manufacturing will soon emerge".

These include a range of new technological solutions, including lighter foam-based concretes that require less energy to produce, and products like CeramiCrete, which is twice as strong so builders use less of it. But all cost more.

The slickest of these new solutions and, ultimately, one that could be produced most cheaply, comes from the unlikeliest quarter of all. A viable alternative to cement is actually being produced by the oil industry.

In a smart, regency-decorated office in Mayfair, sandwiched between the bespoke tailors of Savile Row and the swanky art galleries of Cork Street, Geir Robinson is talking about how a waste product from the oil refinement process could be used to cut our dependence on cement. Robinson is the director of UKM, a partner of Shell, the Anglo-Dutch oil giant that holds the patent to a new substance that, in its own way, could be as radical as Joseph Aspdin's.

Robinson is enthusing about something called C-Fix, sometimes referred to as carbon concrete, a "thermoplastic" heavy-duty binder developed by Shell and the University of Delft and already in use on the two busiest roads in the Netherlands. It is suitable, he says, for replacing 90% of concrete and asphalt applications. But it is the environmental benefits that excite him. "Three-and-a-half tons of carbon dioxide is saved by using a ton of carbon concrete rather than regular concrete," he beams.

Environmental benefits

This seemingly gravity-defying equation stems from the fact that the environmental benefits of C-Fix are twofold. "To produce a road, or a sea defence, and not use cement as a binding agent obviously stops that cement being produced, which stops the carbon from the cement production entering the atmosphere," Robinson says. The other benefit comes from making a practical use of what would otherwise be waste.

It works like this. When crude oil is "cracked" into its components, the top of the refinement process produces petrol, followed by diesel, light fuel oil and then heavy fuel oil. At the bottom of the barrel lies a "fraction" of blackened waste material. It is hard and sticky and of scant economic worth.

"The standard way of dealing with this low-grade oil is to mix it with light fuel oil to make more heavy fuel oil," says Robinson, sketching a diagram of the process on a notepad. "It gets burnt off and doesn't have to be treated as a waste. But that burning causes further CO2 emissions that cause global warming."

Robinson, an environmental scientist and former management consultant with Arthur Andersen, is earnest about its limitations. "In our wildest dreams we don't think we will replace concrete. But in certain applications where concrete isn't as good, like in heavy industrial roads or in salt water environments, we can replace it. That would in itself be fantastic for the environment."

The cement industry knows it faces huge environmental issues. Faced with spiralling fuel costs - more than 40% of the cost of cement comes from firing the kilns - it has worked hard to reduce its emissions. Last November the industry toasted its latest progress report at a House of Commons reception hosted by the Liberal Democrat MP Lembit Opik.

According to Liezel Tipper of the British Cement Association, rather than denigrate concrete we should embrace its own environmental credentials. Concrete's high thermal mass (making it hard to heat or cool) becomes relevant, as less energy is required to heat or cool buildings. "This reduces the need for air conditioning, which uses energy and releases more carbon dioxide," she says.

The trouble is, a modern cement kiln is, for the wider environment, the equivalent of having a cigarette permanently at your lips. Not only do modern plants consume as much energy as a small town; the kilns exhale clouds of toxic organic chemicals, such as dioxins and furans and various, possibly life-threatening, hydrocarbon compounds.

Acid gases generated by the immense heat of the combustion process, billow into the atmosphere, adding a further raft of heavy metals - lead, mercury, cadmium, chromium - to the toxic curl. These pollutants spewing from the stacks are joined by large amounts of dust and gas from the plant operations; and cement mixers guzzle a lot of petrol.

It is a filthy brew, redolent of what has gone wrong with industrialisation: environmentally and financially expensive and linked in several medical reports to the aggravation of lung complaints, especially asthma or emphysema. It is, however, the necessary price we continue to pay to progress in this late industrial age.

Carbon concrete, by contrast, has few of these disadvantages - if you discount the refinement process, itself a recidivist contributor to the great bank of carbon dioxide in the sky. To accept C-Fix is to accept that the oil is going to be pulled out of the ground regardless, so why not burn as little as possible. As Robinson says: "If just a tiny fraction of crude oil were sequestered in this way, western countries would be able to bring their carbon emission reduction in line with the Kyoto Agreement."

Cautious approval

Though any use of the waste products of oil refinement makes most environmentalists nervous, a few are prepared to cautiously endorse some of C-Fix's promise. David Santillo, a Greenpeace senior scientist based at its research laboratory in Exeter, welcomes the oil industry's attempt to crack the cement problem. Although he notes it is "early days to be making any substantial claims about universal applicability," he says the reductions it could bring in CO2 emissions by reducing cement production "are certainly worth exploring in more detail by government departments and contractors." But, he adds, "it will need to be backed by further independent research into its long-term structural stability and environmental performance before it can be promoted widely."

C-Fix's next big push is into the Arab states, rich in oil refineries and new building developments, but desperately short of fresh water and of the right kind of sand: because desert sand has the wrong characteristics, such areas have to import the sand needed to make traditional concrete.

But it is in Holland where C-Fix's most immediate application is most telling. It is being deployed at Ijmuidem harbour as a massive breakwater defence north of Haarlem. Six house-sized blocks of carbon concrete are currently holding the North Sea at bay. If successful, an awful lot more of it will be used along the flat coast of the Netherlands.

That's right: the thing that might keep back the rising tides caused by global warming could be a waste product from the oil refineries that helped cause it.

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